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18 Cards in this Set
- Front
- Back
What are the 4 mechanisms by which anti-arrythmic drugs reduce spontaneous discharge in automatic tissues?
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1. Decrease phase 4 slope
2. Increase threshold for AP firing 3. Increase Vmax 4. Increase AP duration |
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What happens when you block Na channels?
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-Decrease membrane responsiveness
-Increase threshold |
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What happens when you block K channels?
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-Increase ERP
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What happens when you open K channels?
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-Shorten AP duration
-Decrease ERP |
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How do B-blockers affect conduction?
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-Decrease the rate of diastolic depolarization
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What happens when you block L-type Ca channels?
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-Decrease membrane responsiveness
-Increase threshold |
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How many classes of anti-arrythmic drugs are there?
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4
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What are the four classes of anti-arrythmic drugs?
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1. Sodium channel blockers
2. Beta-blockers 3. K blockers 4. Calcium blockers |
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What are the 4 class I drugs?
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1A - Quinidine/Disopyramide
1B - Lidocaine 1C - Flecainide |
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What is the class II drug?
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Propanolol
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What are the 2 Class III drugs?
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-Amiodarone
-Sotalol |
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What are the 2 class IV drugs?
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-Verapamil
-Diltiazem |
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Class IA drugs are ____ and their mechanism is ______:
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-Quinidine/Disopyramide
-Blocks Na channels to moderately depress phase-0 and slow conduction -Blocks K channels to prolong repolarization |
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Class IB drug is ____ and its mechanism is ______:
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-Lidocaine
-Blocks Na channels to minimally depress phase-0 and slow conduction -Opens K channels to shorten repolarization |
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Class IC drug is ____ and its mechanism is ______:
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-Flecainide
-Blocks Na channels to MARKEDLY depress phase 0 and slow conduction -Doesn't do anything to K channels or repolarization |
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So the rank of Class I sodium channel blockers in degree of depression of phase-0 is:
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1A - Quinidine/Disopyr 2+
1B - Lidocaine 1+ 1C - Flecainide 4+ |
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How does blocking Na channels slow conduction velocity?
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By reducing the number of available Na channels, the membrane responsiveness is reduced.
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And what effect does reduced membrane responsiveness have?
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Reduced phase4 diastolic depolarization
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